Natural and synthetic vitamins have been extensively used in various types of skin and cosmetic compositions. Although different methods have been proposed for entrapping and formulating vitamins into skin and cosmetic compositions, the known methods typically require the use of an anhydrous composition or a water-in-organic oil emulsion, both of which are greasy, and therefore cosmetically less appealing. In other instances, the known methods employ a very complicated stabilization system, when one desires to form a less greasy oil-in-water emulsion.
The present invention, in contrast, is based upon an elastomeric silicone polyether which can be used to entrap and formulate vitamins into skin and cosmetic compositions, and which can be used to form less greasy water-in-oil emulsions without requiring additional surfactants. This can be of considerable value in the personal care arena where skin sensitivity due to the presence of certain surfactants can be an issue. The method of making the vitamin entrapped compositions according to this invention is simple, and it does not require the use of high shear or heating. In addition, the elastomeric silicone polyether is capable of providing aesthetic benefits.
While U.S. Pat. 5,811,487 (Sep. 22, 1998), assigned to the same assignee as the present invention, broadly suggests that vitamins can be delivered with an elastomeric silicone polyether, the elastomeric silicone polyether in the '487 patent may contain anywhere from zero to 100 ethylene oxide (EO) units in its molecule. According to this present invention, however, it has been unexpectedly discovered that effective vitamin delivery can only be accomplished by using an elastomeric silicone polyether containing 4-30 (EO) units in its molecule. Moreover, in the case of vitamin A, there is required 7-30, rather than 4-30 (EO) units. This improved performance in a range within the range of the '487 patent is unexpected.
Furthermore, and according to this invention, it has also been unexpectedly discovered that effective vitamin delivery can only be accomplished by using an elastomeric silicone polyether prepared according to a method in which the equivalent ratio of the .tbd.SiH in the .tbd.SiH containing polysiloxane with polyether groups and the unsaturated hydrocarbon is 2:1 to 1:2. In contrast, the '487 patent employs an elastomeric silicone polyether prepared according to a method in which the equivalent ratio of the .tbd.SiH in the .tbd.SiH containing polysiloxane with polyether groups and the unsaturated hydrocarbon is 20:1 to 1:20. Again, improved performance in a range within the range of the '487 patent is unexpected.
In addition, nothing in the '487 patent suggests that oil-soluble vitamins such as vitamin A and vitamin E can be entrapped in the oil phase of elastomeric silicone polyethers.